Adjustable attachment device in a microtome

ABSTRACT

The purpose of the present invention is to provide in a microtome an adjustable attachment for the specimen holder or for the knife, whereby the attachment is designed in a way that the adjustment can be accomplished in two planes at the same time without altering the distance between the specimen and the knife during the adjustment.

nited States Patent [191 Wistedt ADJUSTABLE ATTACHMENT DEVICE IN A MICROTOME [75] Inventor: Karl-Erik Wistedt, Jakobsberg,

Sweden [73] Assignee: LKB-Produkter AB, Bromma,

Sweden [22] Filed: Dec. 14, 1971 [21] Appl. No.: 207,932

[30] Foreign Application Priority Data Dec. 30, 1970 Sweden 17725/70 Nov. 19, 1971 Sweden 14796/71 [52] [1.8. Cl 83/648, 83/699, 83/9155 [51] Int. Cl. Goln U116 [58] Field of Search 83/699, 915.5, 648; 269/75 Uct.9,]1973 [56] References Cited UNITED STATES PATENTS 2,212,953 8/1940 Popp et a1 83/9155 X 2,590,725 3/1952 Sanger 83/9155 X 2,796,788 6/1957 Bohn..... 269/75 2,993,395 7/1961 Bohn 269/75 Primary Examiner-J. M. Meister Attorney-George H. Mitchell, Jr.

[5 7] ABSTRACT The purpose of the present invention is to provide in a microtome an adjustable attachment for the specimen holder or for the knife, whereby the attachment is designed in a way that the adjustment can be accomplished in two planes at the same time without altering the distance between the specimen and the knife during the adjustment.

12 Claims, 2 Drawing Figures PATENTEDUBI 91m FIG. 2

ADJUSTABLE ATTACHMENT DEVICE IN A MICROTOME The present invention relates to a device in a microtome for adjustable attachment of at least either of the knife of the microtome and the specimen, which is to be sectioned, respectively.

When a specimen is sectioned in a microtome, the specimen is usually embedded at the top of a specimen block which at sectioning is conveyed towards a knifeedge. The specimen block then is attached to a specimen arm which is conveying the specimen down towards the knife and which is performing the feed, requisite for the sectioning. The exceedingly thin sections which are obtained are then used in the investigation of the specimen in an electron microscope. The sectioning is preceeded by a so called trimming which implies cutting from the top of the specimen block that part which contains the specimen in that way that e.g. a truncated pyramid is obtained, in the center of which the specimen is situated. The position of the pyramid then depends on how the specimen is situated at the embedding. To make possible to make a section parallel to the pyramid base, the specimen block and hence the specimen must be turnable in relation to the knifeedge. It is also very essential that the distance between the knife-edge and the specimen is not altered during the turning since it is often desired, at least at the first sections, to turn the specimen between subsequent sectionings. An example of how the turning of the specimen can be accomplished is shown in the Swedish Pat. 180,777. The specimen holder is then attached to a segment of a circle, in the central point of which the specimen is situated. The segment of circle is, however, turnable about the specimen arm. The adjustment is carried out by conveying the specimen holder to the desired position on the segment of circle, attaching the specimen in this position by means of a set screw, after which the segment is turned about the specimen arm in order that the specimen becomes oriented in a suitable way in reiation to the knife-edge. This position is then fixed by means of a set screw as well. It appears, however, that the adjustment in one direction has influence on the previously made adjustment in the other direction. Among other things the position of the specimen is slightly dislodged when the set screw is drawn. Thus, it might be necessary to make a great number of adjustments in the two directions alternately. Some type of attachment in which the adjustment can be accomplished in both directions in one step would then be desirable to eliminate this drawback. This can be obtained by some sort of a ball joint. In order that the distance between the specimen and the knife should then not be altered when the ball is turned, the specimen must, however, be in the center of the ball. For the attachment of the ball it is required that the attachment of the ball is covering more than half of the surface of the ball which fact makes this placing of the specimen impossible.

Hence the purpose of the present invention is to provide in a microtome an adjustable attachment for the specimen holder or for the knife, whereby the attachment is designed in a way that the adjustment can be accomplished in two planes at the same time without altering the distance between the specimen and the knife during the adjustment.

The invention will now be further explained with reference to the attached drawing in which: FIG. 1 shows an axial, longitudinal section of a specimen attachment according to the invention, and

FIG. 2 shows the attachment, viewed from the knife.

In FIG. I, 1 denotes a specimen which is embedded at the top of a specimen block 2, which is attached in a specimen holder 3. The specimen holder 3, which has a spherical base, is made of a magnetically conducting material and is in close contact with two cylindrical, concentric pole pieces 4 and 5 respectively, the end faces of which are designed in a way that a good contact is obtained to the spherical surface of the specimen holder. The central pole piece 5 is through an air gap 12 coupled to one pole of a permanent magnet 7, the other pole of which is in close contact with a piece of soft iron 6, which in its turn is in close contact with the pole piece 4. The field from the permanent magnet 7 is thus closed through the air gap 12, the pole piece 5, the specimen holder 3, the pole piece 4 and the piece of soft iron 6. In order to delimit the stray flux between the pole pieces, the layer 8 between the pole pieces, requisite for the mechanical stability, is made of e.g. brass or nylon. The permanent magnet 7 and the soft iron piece 6 are displaceable in axial direction in order that the air gap 12 is altered by means of turning a ring 9, which is screwed in the pole piece 4, whereby two rods 10 are moved along the axis of the attachment. These rods are in close contact with two pins 1 l, which are driven into the soft iron piece 6. When the ring is turned outwards, the magnet 7 will thus by the magnet force be displaced in a way that the air gap 12 between the magnet and the pole piece 5 will be reduced, whereby the force which is holding the specimen holder 3 is increased. The hitherto described device is arranged at the end of a specimen arm, not shown in the drawing, and may by this one be conveyed up and down in the drawing. When the specimen is conveyed downwards against a knife 13, hinted in the figure, a section is detached from the surface of the specimen top.

In FIG. 2 the specimen attachment is showed viewed from the knife. The same notations are used as in FIG. 1. As is obvious from FIG. 2 the ring 9 is along its outer periphery equipped with notches in order to make the ring easily turnable, when it is desired to alter the magnet force. It is further obvious from the drawing that the edge of the specimen holder 3 has a mainly square form. The purpose thereof is to provide a good grip at adjustments of the position.

When the specimen is to be turned to an angle, suitable in relation to the knife, the specimen holder is turned in its spherical attachment. During the turning the holder will all the time be in close contact with the attachment, and consequently the specimen, which is oriented in a way that it is in the center of the spherical attachment, does not alter its distance to the knife but is only turned in relation to this one. At the turning only the frictional drag, generated from the magnetic force, is to be counteracted. The friction coefficient is thus selected in a way that the tangential force is not greater than that it may conveniently be overcome by hand. When a desired position has been adjusted, the sectioning itself may start, which as mentioned above is accomplished in that way that the specimen is conveyed down past the knife-edge and then again is lifted past the knife-edge. During the retrograde motion either the knife or the specimen is taken aside. At sectioning the specimen will among other things be subject to a vertical force when the knife is hitting the specimen. This force, however, gives rise to tractive and compressive forces at the attachment surface of the specimen holder. The magnetic force may, however, even by means of relatively small magnets, be made sufficiently great in order that the specimen holder is not broken loose. At the device according to the invention it is thus necessary only to overcome the frictional forces while the essentially greater tractive forces of the magnet are employed at sectioning itself.

Even though a requisite tractive force of the magnet is normally consistent with a shearing force which is so small that the attachment can be displaced, it may in certain cases be desirable to increase the tractive force further. For this purpose the permanent magnet 7 is, as mentioned above, axially moveable in order that a variable air gap 12 can be obtained. The displacement is achieved by turning the ring 9. it is thus possible to make the adjustment with a relatively big air gap and then, before the sectioning itself is started, decrease the air gap without dislodging the specimen in order that a greater traction force is obtained between the attachment and the holder. At adjustment of the position of the specimen it is often desirable to have the possibility of applying the specimen in a predestinated position which at earlier sectionings has showed to be the optimal one. For this purpose the spherical surface of the specimen holder 3 is provided with two perpendicular scales and the outer surface of the pole piece 4 with suitable indications towards which a certain point in the scale system could be adjusted.

It will be appreciated that the knife of the microtome might as well be affixed in an adjustable attachment according to the present invention. When, according to this embodiment of the present invention, the knife, affixed in the holder, is to be turned to an angle, suitable in relation to the specimen, the knife holder is turned in its spherical attachment. During the turning the holder will all the time be in close contact with the attachment, and consequently the knife-edge, provided that it is oriented in a way that its middle is in the center of the spherical attachment, does not alter its distance to the specimen, but is only turned in relation to this one.

It will be appreciated that both the specimen and the knife might aeach be situated in a device according to the present invention.

The purpose of the present invention is thus accomplished in that way that the holder for at least either of the knife of the microtome and the specimen, which is to be sectioned, respectively, is designed as a magnet holder, as described above.

At a device according to the present invention it is of course also possible to choose a cylindrical base surface at the holder 3. In this embodiment, however, possibility of adjustment is at hand only in one plane. If the top of the specimen or the knife-edge is on the axis of the cylindrical surface, the turning will not cause any distance change between the specimen and the knife.

We claim:

1. In a microtome of the type wherein two elements are arranged to be conveyed relative to each other in a linear path to section a specimen and in which the relative angular positions of said two elements is universally adjustable, said two elements including a knife and a support for a specimen, the improvement which includes a holder for at least one of said two elements comprising magnetic material, said holder being provided with a semi-spherical supporting surface, means to mount said one element substantially at the center of curvature of said semi-spherical surface, a pair of concentric pole pieces comrpising magnetic material terminating at their one ends in a semi-spherically recessed surface complementary to the semi-spherical surface of said holder and in universally slidable engagement therewith for universally angularly orienting said one element, said holder and said pair of pole pieces comprising a portion of a magnetic circuit, and permanent magnet means having poles of opposite polarity mounted to complete said magnetic circuit through said pair of pole pieces.

2. The invention defined in claim 1, wherein said one element comprises a support for a specimen to be sectioned.

3. The invention defined in claim 1, wherein said one element comprises a knife for sectioning a specimen, the center of the knife edge being positioned at the center of curvature of said semi-spherical surface.

4. The invention defined in claim 1, wherein the attractive force between said semi-spherical surface and the semi-spherical supporting surface is sufficient to retain said one element in fixed position during operation of the microtome but insufficient to prevent manual readjustment of said fixed position.

5. The invention defined in claim 4, wherein said one element comrpises a support for a specimen to be sectioned 6. The invention defined in claim 4, wherein said one element comprises a knife for sectioning a specimen, the center of the knife edge being positioned at the center of curvature of said semi-spherical surface.

7. The invention defined in claim 1, wherein said permanent magnet means includes means to adjust the relative position between one of said concentric pole pieces and one of the poles of the permanent magnet means to vary the magnetic force between the pole pieces and said holder.

8. The invention defined in claim 7, wherein said one element comprises a support for a specimen to be sectioned.

9. The invention defined in claim 7, wherein said one element comprises a knife for sectioning a specimen, the center of the knife edge being positioned at the center of curvature of said semi-spherical surface.

10. The invention defined in claim 7, wherein one of the poles of said pennanent magnet means is mounted in axial alignment with one of said pole pieces and includes means to shift said one pole toward and away from said one pole piece.

11. The invention defined in claim 10, wherein said one element comprises a support for a specimen to be sectioned.

12. The invention defined in claim 10, wherein said one element comprises a knife for sectioning a specimen, the center of the knife edge being positioned at the center of curvature of said semi-spherical surface. i i 

1. In a microtome of the type wherein two elements are arranged to be conveyed relative to each other in a linear path to section a specimen and in which the relative angular positions of said two elements is universally adjustable, said two elements including a knife and a support for a specimen, the improvement which includes a holder for at least one of said two elements comprising magnetic material, said holder being provided with a semi-spherical supporting surface, means to mount said one element substantially at the center of curvature of said semispherical surface, a pair of concentric pole pieces comrpising magnetic material terminating at their one ends in a semispherically recessed surface complementary to the semi-spherical surface of said holder and in universally slidable engagement therewith for universally angularly orienting said one element, said holder and said pair of pole pieces comprising a portion of a magnetic circuit, and permanent magnet means having poles of opposite polarity mounted to complete said magnetic circuit through said pair of pole pieces.
 2. The invention defined in claim 1, wherein said one element comprises a support for a specimen to be sectioned.
 3. The invention defined in claim 1, wherein said one element comprises a knife for sectioning a specimen, the center of the knife edge being positioned at the center of curvature of said semi-spherical surface.
 4. The invention defined in claim 1, wherein the attractive force between said semi-spherical surface and the semi-spherical supporting surface is sufficient to retain said one element in fixed position during operation of the microtome but insufficient to prevent manual readjustment of said fixed position.
 5. The invention defined in claim 4, wherein said one element comrpises a support for a specimen to be sectioned
 6. The invention defined in claim 4, wherein said one element comprises a knife for sectioning a specimen, the center of the knife edge being positioned at the center of curvature of said semi-spherical surface.
 7. The invention defined in claim 1, wherein said permanent magnet means includes means to adjust the relative position between one of said concentric pole pieces and one of the poles of the permanent magnet means to vary the magnetic force between the pole pieces and said holder.
 8. The invention defined in claim 7, wherein said one element comprises a support for a specimen to be sectioned.
 9. The invention defined in claim 7, wherein said one element comprises a knife for sectioning a specimen, the center of the knife edge being positioned at the center of curvature of said semi-spherical surface.
 10. The invention defined in claim 7, wherein one of the poles of said permanent magnet means is mounted in axial alignment with one of said pole pieces and includes means to shift said one pole toward and away from said one pole piece.
 11. The invention defined in claim 10, wherein said one element comprises a support for a specimen to be sectioned.
 12. The invention defined in claim 10, wherein said one element comprises a knife for sectioning a specimen, the center of the knife edge being positioned at the center of curvature of said semi-spherical surface. 